feat: 新增 jsc-matt 外掛，收錄 Matt Pocock 全套技能，指令為 /jsc-matt:*

- 改編自 mattpocock/skills 1.2.3（MIT），含 engineering 與 productivity 共 25 個技能
- 技能間的呼叫名稱一律加上 jsc-matt: 前綴
- marketplace 與 README 補上 jsc-matt

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

plugins/jsc-matt/skills/engineering/implement/SKILL.md

@@ -0,0 +1,15 @@
+---
+name: implement
+description: "Implement a piece of work based on a spec or set of tickets."
+disable-model-invocation: true
+---
+
+Implement the work described by the user in the spec or tickets.
+
+Use /jsc-matt:tdd where possible, at pre-agreed seams.
+
+Run typechecking regularly, single test files regularly, and the full test suite once at the end.
+
+Once done, use /jsc-matt:code-review to review the work.
+
+Commit your work to the current branch.

plugins/jsc-matt/skills/engineering/implement/agents/openai.yaml

@@ -0,0 +1,5 @@
+interface:
+  display_name: "Implement"
+  short_description: "Build work from a spec or tickets"
+policy:
+  allow_implicit_invocation: false